Ph.D. University of California, Berkeley. Chemical Engineering. 1996.
B.S. University of Wisconsin, Madison. Chemical Engineering. 1990.
B.S. University of Wisconsin, Madison. Economics. 1990.
Our research investigates complex fluids – soft materials with properties intermediate between fluids and solids. Our current interests include nanocolloidal assembly, colloidal gelation, and the biomechanics of bacterial biofilms. Applications that interest us include creating new optical materials, sensors, biomedical devices and procedures, as well as materials for energy management.
The assembly of nanocolloids into useful structures has long been a key aim of chemical engineers and materials scientists. Yet, the success of this technological aim is severely hindered by some deep fundamental problems. We address this challenge by synthesizing anisotropic colloids and assembling them with the assistance of applied electric, shear and gravitational fields. In a second effort, we address the fact that the typical size of the ordered arrays that have been produced in academia is currently too small for real-world applications. We have investigated the complex fluid dynamics of large-scale methods for colloidal crystal production, such as spin coating. These questions are studied within a collaborative, student-drive research program that includes novel colloid synthesis, direct visualization of assembly structure and dynamics by confocal microscopy as well as rheological measurements.
Colloidal gelation is a common industrial process to manage the rheological and microstructural properties of complex fluid formulations used in the stabilization of consumer products, ceramic materials and pharmaceutical formulations. By developing new 3D confocal microscopy methods, our group has made fundamental discoveries about gels that are currently being applied in industry to develop new materials and complex fluid processing methods. Currently, we are engaged in an investigation of the origin of rupture and yielding in colloidal gels. The work involves a combination of advanced microscopy techniques, flow cell fabrication using methods such as microfabrication, and rheological measurements.
We also explore the biomechanical properties of bacterial biofilms. Biofilms are colonies of microorganisms that are pervasive in a range of natural and industrial settings. They can also grow on devices, such as intravascular catheters, that are introduced into the body as part of medical practice. Biofilm structure and mechanics is thought to play a protective role by, for example, improving the resistance of bacteria to antibiotic treatments. The aim of this project is to understand and measure the mechanical properties of biofilms of size about 10 - 100 microns, since these dimensions match the scales relevant to medical practice. As part of this work, we have developed a flexible microfluidic rheometer for micromechanical measurements of bacterial biofilm elasticity. Current work is focused on molecular characterization of the extracellular polysaccharides present in biofilms, rheological characterization of whole biofilms, and confocal microscopy visualization of the complex microscopic structure of biofilms.
Solomon, M.J., “Directions for targeted self-assembly of anisotropic colloids from statistical thermodynamics,” Current Opinion in Colloid Interface Science, in press (2011).
Dzul, S.P., M.M. Thornton, D.N. Hohne, D.M. Bortz, M.J. Solomon and J.G. Younger, “Contribution of the Klebsiella pneumoniae Capsule to Bacterial Community Microstructure Determined With High-Resolution Confocal Microscopy,” Applied and Environmental Microbiology in press (2011).
Bryne, E., D.M. Bortz, S. Dzul, M.J. Solomon and J. Younger, “Postfragmentation density function for bacterial aggregates in laminar flow,” Phys. Rev E. in press (2011).
Mukhija, D. and M.J. Solomon, “Nematic order in suspensions of colloidal rods by application of a centrifugal field,” Soft Matter, 7 540-545 (2011).
Elbing, B., M.J. Solomon, M. Perlin, D. Dowling and S.L. Ceccio, “Degradation of Drag-Reducing Polymer Solutions within a High-Reynolds Number Turbulent Boundary Layer,” J. Fluid Mechanics 670 337-364 (2011).
Shereda, L.T., R.G. Larson, and M.J. Solomon, “Shear banding in crystallizing colloidal suspensions,” Korea-Australia Rheology Journal 22(4) 309-316 (2010).
Shereda, L.T., R.G. Larson, and M.J. Solomon, “Boundary-driven colloidal crystallization in simple shear flow,” Physical Review Letters, 105 228302 (2010).